The present invention relates to apparatus and methods for carrying out entity detection and verification in a raster system including a store for data. More particularly it provides for entity detection and verification in bit mapped raster graphic systems.
Various systems for enhancing the presentations of selected displays have been suggested. In such systems encoded information is fed into a storage memory where it's stored. When needed the encoded information is selectively read out of the memory, decoded and used to control the beam of a cathode ray or video display tube to form an image such as a line or a circle or the like on the face of the tube.
Basically there are two types of video display tubes. One tube employs a vector display arrangement and the other employs a raster display. In the vector display, the electron gun constantly emits a beam which is then caused to trace the displayed image. In the raster scan system the beam is modulated in intensity while the screen is scanned, i.e., the beam position is deflected in a definite regular pattern across the face of the tube so that in effect an array of spots of varying intensity or colors are used to form the image. Each full pattern covering the entire display is known as a frame.
In vector display systems entity detection is dependent on the image being serially regenerated from a memory. The methods for performing entity identification and verification are well known to the art and are not described herein.
In raster display systems entity detection has also been accomplished by a regenerating image memory, however, such a system requires very fast and expensive rasterization equipment and limits the graphics order buffer size.
Each feature of an image on a raster display is formed of a string of picture elements or pixels. Each pixel displayed has a particular address and is formed by one or more bits stored in a memory. The bits are used to form each pixel by controlling the intensity and/or color of the beam used to form the pixel.
In a typical prior art three electron gun color raster system, the bits used to form each pixel are used in one of two ways. In the first way, the bits are subdivided into three groups, each group controlling directly one of the electron guns in the CRT. In the second way the bits are used as an index in a "color look-up table." In this case, each entry in the look-up table contains the sets of bits used to control the electron guns in the CRT.
In both types of prior art color raster systems, once the image memory is defined, there is no way of knowing whether a particular pixel is associated with any particular feature of the image being displayed (i.e., whether a pixel is part of the image background, or part of a particular line, etc.) without regenerating image memory.
Accordingly, the present invention is designed to overcome the difficulties encountered in the prior art apparatus and permits entity detection and entity verification, i.e., emphasizing the detected entity, in real time without requiring image memory regeneration, fast or expensive rasterization equipment and without graphic order size limitations.